<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app"></div>

    <template id="my-app">
      <div>
        <h2>{{message}}</h2>
        <component-a></component-a>
      </div>
    </template>

    <template id="component-a">
        <h2>我是组件A</h2>
    </template>

    <script src="../vue/vue.js"></script>
    <script>
        const ComponentA = {
            template: '#component-a'
        }

        const App = {
            template: '#my-app',
            components: {
                // key: 组件名称
                // value:组件对象
                ComponentA: ComponentA
                // ComponentA
            },
            data() {
                return {
                    message: 'hello '
                }
            }
        }

        const app = Vue.createApp(App);
        // app.component('ComponentA', ComponentA)
        app.mount('#app');
    </script>
</body>
</html>